Facades

简介

Facades 提供了一个“静态”接口到 IoC 容器 类 。Laravel 含有很多 facades,你可能不知道你在某些地方已经使用过它们了。

有时候, 你可能想为你的应用程序或包创建自己的 facades, 所以,让我们来讨论一下如何开发和使用这些类。

注意 在深入 facades 之前,我们强烈建议你多了解一下 Laravel Ioc 容器

说明

在 Laravel 应用程序中, facade 是提供从容器中访问对象方法的类。Facade 类实现了该机制。

你的 facade 类只需要实现一个方法: getFacadeAccesorgetFacadeAccessor 方法的工作是定义如何从容器中取得对象。 Facades 基类构建了 __callStatic() 魔术方法来从 facade 延迟访问取得对象。

So, when you make a facade call like Cache::get, Laravel resolves the Cache manager class out of the IoC container and calls the get method on the class. In technical terms, Laravel Facades are a convenient syntax for using the Laravel IoC container as a service locator.

实际用例

在以下示例中,执行 Laravel 缓存系统, 查看该代码,我们可能会假定 get 静态方法是执行在 Cache 类。

In the example below, a call is made to the Laravel cache system. By glancing at this code, one might assume that the static method get is being called on the Cache class.

$value = Cache::get('key');

然后,如果我们查看 Illuminate\Support\Facades\Cache 类, 你会发现该类没有任何 get 静态方法:

class Cache extends Facade {

    /**
     * Get the registered name of the component.
     *
     * @return string
     */
    protected static function getFacadeAccessor() { return 'cache'; }

}

Cache 类继承基本 Facade 类,并且定义了个 getFacadeAccessor() 方法。注意,该方法的工作是返回 IoC 绑定的名字。

当用户引用任何在 Cache facade 静态方法, Laravel 从 IoC 容器绑定中取得 cache,并且执行请求该对象方法(在该例子中为get)。

所以,我们 Cache::get 执行可以重写为:

$value = $app->make('cache')->get('key');

创建 Facades

要为自己的应用程序或者包创建一个 facade 是非常简单的。你需要做三件事情:

让我们来看个例子。这里,我们定义一个 PaymentGateway\Payment 类。

namespace PaymentGateway;

class Payment {

    public function process()
    {
        //
    }

}

This class might live in your app/models directory, or any other directory that Composer knows how to auto-load.

我们需要能够在 IoC 容器中取得该类。所以,让我们增加一个绑定:

App::bind('payment', function()
{
    return new \PaymentGateway\Payment;
});

最好注册该绑定的位置是创建一个新的名为 PaymentServiceProvider 服务提供器,并且将该绑定加入到 register 方法。接下来你就可以配置 Laravel app/config/app.php 配置文件来加载该服务提供器。

接下来,我们就可以创建我们的 facade 类:

use Illuminate\Support\Facades\Facade;

class Payment extends Facade {

    protected static function getFacadeAccessor() { return 'payment'; }

}

最后,如果你想,我们可以为我们 facade 设置别名到 app/config/app.php 配置文件里的 aliases 数组。现在,我们能够调用 Payment 类实例的 process 方法。 Payment::process();

模拟 Facades

单元测试是 facades 工作的重要体现。事实上,可测试性是 facedes 存在的主要原因。要了解更多信息,查看文档模拟 facades部分。

Facade Class Reference

Below you will find every facade and its underlying class. This is a useful tool for quickly digging into the API documentation for a given facade root. The IoC binding key is also included where applicable.

Facade Class IoC Binding
App Illuminate\Foundation\Application app
Artisan Illuminate\Console\Application artisan
Auth Illuminate\Auth\AuthManager auth
Auth (Instance) Illuminate\Auth\Guard
Blade Illuminate\View\Compilers\BladeCompiler blade.compiler
Cache Illuminate\Cache\Repository cache
Config Illuminate\Config\Repository config
Cookie Illuminate\Cookie\CookieJar cookie
Crypt Illuminate\Encryption\Encrypter encrypter
DB Illuminate\Database\DatabaseManager db
DB (Instance) Illuminate\Database\Connection
Event Illuminate\Events\Dispatcher events
File Illuminate\Filesystem\Filesystem files
Form Illuminate\Html\FormBuilder form
Hash Illuminate\Hashing\HasherInterface hash
HTML Illuminate\Html\HtmlBuilder html
Input Illuminate\Http\Request request
Lang Illuminate\Translation\Translator translator
Log Illuminate\Log\Writer log
Mail Illuminate\Mail\Mailer mailer
Paginator Illuminate\Pagination\Environment paginator
Paginator (Instance) Illuminate\Pagination\Paginator
Password Illuminate\Auth\Reminders\PasswordBroker auth.reminder
Queue Illuminate\Queue\QueueManager queue
Queue (Instance) Illuminate\Queue\QueueInterface
Queue (Base Class) Illuminate\Queue\Queue
Redirect Illuminate\Routing\Redirector redirect
Redis Illuminate\Redis\Database redis
Request Illuminate\Http\Request request
Response Illuminate\Support\Facades\Response
Route Illuminate\Routing\Router router
Schema Illuminate\Database\Schema\Blueprint
Session Illuminate\Session\SessionManager session
Session (Instance) Illuminate\Session\Store
SSH Illuminate\Remote\RemoteManager remote
SSH (Instance) Illuminate\Remote\Connection
URL Illuminate\Routing\UrlGenerator url
Validator Illuminate\Validation\Factory validator
Validator (Instance) Illuminate\Validation\Validator
View Illuminate\View\Environment view
View (Instance) Illuminate\View\View